Bite The Bullet
Snipers: A Tight Fit (2009-06-05)
Snipers: a tight fit
For snipers, every little bit of accuracy helps. and the one of the most common upgrades found on a sniper rifle is an aftermarket precision barrel. But it is often disputed how effective these barrels are, and how tight is too tight.
The key factor is the space between the bb and the barrel. The more contact the BB makes with the barrel as it goes through it the more disruption there is to the hop-up. Therefore the tighter you go, eventually, the benefits of a tighter barrel become overshadowed by the downside of having too much disruption to the BB's backspin. There is a plus side though, the less space between the barrel and the BB the better seal the BB makes against the barrel and thus more efficiently turns the pressure behind it into BB exit velocity.
It is also important to use the correct size of BB for your barrel. It may not be to commonly known but different brands and batches of BBs have significantly different sizes of BBs. from 'large' 5.96-5.98mm diameter, to 'small' 5.90mm diameter or even less. For example let's have a look at these three brands of BBs; KSC 'perfect' 0.20g, Tokyo Marui's 0.20g BBs, Excel's 0.20g BB, a Chinese Brand called 'Goldenball' 0.20g, and lastly the new-on-the-market Madbull match grade 0.20g BBs. 15 of each were taken and measured precisely with a vernier caliper, then the average was calculated.
|Chinese (goldenball)||Madbull match grade|
|avg: 5.940 mm||avg: 5.963 mm||
avg: 5.885 mm
|avg: 5.913mm||avg: 5.959mm|
next we calculate the standard deviation for the BB sizes:
|KSC||Tokyo Marui||Excel||Chinese (goldenball)||Madbull match grade|
It turns out that the KSC BBs were a 'medium' 5.940mm, the Tokyo Marui BBs were a larger 5.63mm and the Excel BBs had the most variation but were the smallest at 5.88mm. Goldenball BBs had a similar size variation than Excel but were larger at 5.913mm. Madbull match grade BBs were the most consistent with an amazingly low standard deviation of only 0.009mm.
Another aspect other than accuracy that the variance of BBs will have on the gun is it's power. Consistent power is paramount to accuracy over long ranges as obviously, different powers result in different trajectories. Hypothetically a larger BB should provide a better seal in the barrel and show a marginal increase in velocity. We will also calculate the standard deviation of the velocity of the shots fired in order to show power consistency.
15 shots were fired of each type of BB through a PDI 6.01 tightbore to ensure that the barrel wasn't the cause of the deviation. A spring sniper (Tokyo Marui VSR10 G-Spec) was used as they are many times more consistent than gas sniper rifles. The test was done indoors at 25 degrees Celsius (77 degrees Fahrenheit) and the relative humidity at 82% here is the raw data:
|KSC||Excel||Chinese (goldenball)||Madbull match grade|
|avg: 306.6 fps||avg: 301.1fps||avg: 299.0fps||avg: 300.9fps||avg: 301.2fps|
From these results we can immediately tell that the larger Tokyo Marui BBs made a better seal in the barrel, thus providing higher exit velocities and Excel BBs, being the smallest, had the lowest exit velocities. but only by 7.6fps. Still, this proves that the larger BBs do cause a slight increase in velocity.
Next we calculate the standard deviation for the exit velocities:
|Chinese (goldenball)||Madbull match grade|
As we can se here from the standard deviation results, Tokyo Marui BBs were the most consistent in terms of exit velocities varying an average of only 1.35fps higher or lower. What this means is that on average, the BB's velocity will be 1.35FPS off from the average velocity of all the bbs giving you a very accurate consecutive shots.
From these results we can conclude that out of these three BBs the tokyo marui branded bbs provided the best seal against the barrel as they were largest and were the most consistent in terms of power. KSC 'perfect' BBs followed a close second and the Madbull Match grade BBs were third leaving Excel BBs and chinese Goldenball BBs as the most inconsistent in terms of power. This is probably caused by the texture of the surface of the bb, with Excel being not as polished as goldenball. But measuring polish on the surface of the BB requires equipment we don't have here at redwolf so however it remains to be seen how these BBs handle accuracy and hop-up.